1. Field of the Invention
The invention relates generally to methods and apparatus for providing connectivity between personal computers (PCs) and local area networks (LANs) using standardized packet protocols to transmit data packets over a digital wide area network of synchronous digital lines, including a digital data service (DDS) wide area network, such as a Frame Relay network.
More particularly, the invention relates to methods and apparatus for providing virtual local connection of one PC to another PC, a PC to a LAN and from one LAN to another LAN, over a digital wide area network; effectively enabling a LAN to be extended through a digital wide area network on a virtual basis.
According to one aspect of the invention, the virtual extension of a LAN through a DDS is accomplished using a unique PC adapter card (hereafter referred to as a PC/DDS adapter card) that includes an on board Data Service Unit (DSU)/Channel Service Unit (CSU), driven by control means (which may, according to a preferred embodiment of the invention, be implemented in software running on the PC motherboard microprocessor), that functions at least in part as a LAN interface emulator.
In other words, applications software running on the PC in which the PC/DDS adapter card is installed is made to "think" the PC is directly connected to a LAN via a standard LAN interface card driven by commercially available LAN interface driver software; when in fact the PC is virtually connected to the LAN (or LAN extension) through a DDS network via the novel PC/DDS adapter card interface to the network, with the PC/DDS adapter card being driven by the aforementioned control means (also referred to hereinafter as the "DDS Driver").
Further aspects of the invention are directed to providing methods (and corresponding apparatus) for (a) programming (sometimes referred to as "soft setting"; versus manually setting via dip switches, etc.) the PC/DDS adapter card with interrupt request, Direct Memory Access (DMA) channel, adapter card address, and line speed parameters; (b) establishing connectivity between at least one PC and at least one LAN, each separately connected to the network, via a gateway access thru the DDS network; and
(c) utilizing the PC motherboard microprocessor to run user applications software while simultaneously being able to handle the real time constraints of running packet protocols (e.g., Frame Relay, X.25, SMDS, etc.), using the novel DDS Driver control means.
2. Brief Description of the Prior Art
With the proliferation of PCs, LANs, and bandwidth intensive applications, the need for high-speed connectivity has spread beyond the major data centers, and out to the smallest branch offices. These factors, combined with an improved communications infrastructure, changing demographics, and ever-changing government regulations have lead to an increasing work-at-home/"telecommuting" work force that requires the cost effective ability to access remotely located LANs, host computers, etc., in a manner that, for example, can interoperate with routers that may already exist on a remote corporate network, etc.
One solution to providing the desired connectivity has been to utilize present day modem interconnect technology to provide an asynchronous interface between, for example, a PC and a wide area network, such as the public switched telephone network (PSTN).
Those skilled in the art will recognize that such solutions for providing connectivity are inherently problematic in that asynchronously transmitted data does not take advantage of the superior throughput capability (increased available bandwidth) of existing synchronous digital transmission systems, including digital wide area networks such as a Digital Data Service (DDS) network (for example, a Frame Relay network), which may also be used to interconnect remotely located PCs, LANs, etc.
DDS networks, such as the Frame Relay example, have the further advantage over the normal PSTN of allowing a multitude of devices to share the same bandwidth on an as needed basis without bandwidth being set aside for the exclusive use of any particular device.
Prior art solutions to the connectivity problem using a DDS network are also known.
For example, a PC can be connected to a DDS using a commercially available FX-E1 Data Service Unit (DSU), provided by ISDN Systems Corporation of Vienna, Va.; coupled to a commercially available DE-11 Channel Service Unit (CSU) provided by General Datacom.
A DSU card, exemplified by the aforementioned FX-E1 card, may be inserted as a daughterboard into an existing PC, such as, for example, an IBM PC-AT ("IBM" is a trademark of the International Business Machines Corporation), to take asynchronous parallel data (for example, byte wide data) transmitted over the PC bus and convert the data to a synchronous serial bit stream (such as V.35), which can then be processed by a DDS hardware interface device (such as the DE-11). The interface device provides data to a physical link into a DDS network in accordance with DDS standards, such as those published (and incorporated herein by reference) in AT&T, Technical Reference 62310, "DSO Digital Local Channel--Description and Interface Specification", issued in August of 1993.
The known solutions for providing connectivity between remotely located PCs, LANs, etc., over a DDS network, suffer from one or more of the following problems: (1) a separate DSU and CSU is required to achieve the desired connectivity; (2) present day DSU and CSU devices are costly, cumbersome to install, particularly in home offices, and consume too much space; (3) commercially available DSU cards, including the exemplary FX-E1 card, requires the manual setting of dip switches to, define the card's address in the PC I/O space, define the card's interrupt line on the PC bus and define the card's DMA (Direct Memory Access) channel to the PC microprocessor memory; and (4) prior art DSU and CSU cards are typically required to have a "smart" design, i.e., they are required have a self contained microprocessor and associated memory for managing DSU and CSU functions.
In view of the state of the art as illustrated by the aforementioned devices for achieving connectivity of PCs and LANs through a DDS network, it would be desirable, in general, to provide methods and apparatus which can be used to establish a virtual local connection of one PC to another PC, a PC to a LAN and from one LAN to another LAN, over a DDS (effectively enabling a LAN to be extended through a DDS on a virtual basis); and at the same time solve the aforestated problems.
In particular, it would be desirable to provide methods and apparatus for achieving connectivity between remotely located PCs, LANs, etc., over a DDS network, which utilize a single integrated PC/DDS adapter card, for performing the functions heretofore performed by separate DSUs and CSUs, to effectively extend a LAN to a PC through the network.
Furthermore, it would be desirable to provide methods and apparatus for achieving the aforestated connectivity and LAN extendability objectives with devices that conserve space, are easy to install and are cost efficient solutions to providing virtual connection to remotely located processing resources, particularly for the home office consumer of such resources.
Still further, it would be desirable to provide methods and apparatus for eliminating the requirement of having to manually set the status of switches to define a PC/DDS adapter card's address in PC I/O space, define the card's interrupt line on the PC bus and define the cards DMA (Direct Memory Access) channel to the PC microprocessor memory.
Further yet, it would be desirable to provide a single integrated PC/DDS adapter card, for achieving the aforestated connectivity and LAN extendability objectives, that does not require an onboard microprocessor and/or associated memory for managing the integrated DSU and CSU functions.
It would also be desirable to provide methods and apparatus for accomplishing the virtual extension of a LAN through a DDS using a PC/DDS adapter card that includes an on board Data Service Unit (DSU)/Channel Service Unit (CSU), driven by control means that function at least in part as a LAN interface emulator.
In addition to all the above, it would be desirable to provide methods and apparatus which facilitate operating the PC/DDS adapter card at any one of a plurality of desired (and changeable) line speeds; establish connectivity between at least one PC and at least one LAN, each separately connected to the network, via a gateway access thru the DDS network; support utilizing a PC's motherboard microprocessor to run user applications software while simultaneously being able to handle the real time constraints of running packet protocols (e.g., Frame Relay, X.25, SMDS, etc.), using the aforementioned DDS Driver control means; support a built-in error rate testing capability on the integrated PC/DDS adapter card (configurable via the PC motherboard microprocessor); and make use of industry standard data encapsulation methods (such as, for example, RFC-1490) to insure that the data transmitted by the PC/DDS adapter card contemplated by the invention can interoperate with routers that may already exist on a corporate network.